HELP; could biting cause pink in underwear

Me and my gf were messing around and i accidentally bit a lip of her vagina, could that cause small amounts of pink in her underwear. If not are there any other possibilities of what that pink could be. Her period is late but hers has always been messed up (i.e. it will skip months) we havent had sex but there has been genital contact, just no penetration and no ejaculation. Please Help!!!!!!!!!